Responsive theme and Woocommerce

I know couponpress and woocommerce weren’t really compatible before, especially with couponpress 7 (and below). Now with the new responsive theme (v8) most problems between them are solved, except for one; the search functionality. As far as I can tell, this hasn’t improved as much as I hoped it would.

The thing is… the search widget of woocommerce no longer works with the responsive theme. I receive the following error:

Warning: Illegal offset type in isset or empty in /home/……/wp-includes/post.php on line 1038
When I take a look at the file post.php, it refers to: if ( empty($wp_post_types[$post_type]) )

In ver.7 the search widget of woocommerce worked just fine and it also works properly with a different theme such as Twenty Thirteen or Twelve. So I think the problem is with the responsive theme.
Anyone has any idea on how to solve this? A search functionality of woo commerce products is a necessity that my website can’t live without.

Also, I can’t say this enough but compliments on the new theme! You really have outdone yourself, Mark!